Genetic changes related to carcinogenesis are being studied using hybrids from fusion of human lung carcinoma cells with normal human bronchial epithelial cells and of microcells of individual marked human chromosomes with human lung tumor cells. Initial studies suggest that a limited population doubling potential (mortality) is the dominant genetic trait in hybrid cells. Other hybrid cell lines have been isolated and are being characterized for doubling potential, karyotype and tumorigenicity in athymic nude mice. When specific human chromosomes have been transferred by microcell methodology into HuT 292 cells, chromosome 11 but not chromosome 13 has altered the tumorigenicity of the HuT 292. The location of the putative tumor suppressor gene on chromosome 11 will be determined.